Mongolian spots are flat, deep-brown to slate gray or blue-black patches usually found on the lower back, buttocks, and occasionally on the arms and legs of normal infants. The frequency of these spots varies. They may be seen in about 10 percent of Caucasians to over 90 percent of African-Americans.

These spots are harmless, present at birth, and are made up of large concentrations of the pigment containing skin cells called melanocytes. Because their color can range from black to blue, they may be occasionally be mistaken for bruising which can be embarrassing for parents. These spots generally have some fading over the first two years of life and disappear between the ages of 7 and 13. However, occasionally, they persist into adulthood.